Present invention relates to a method of preparation of 4-aminodiphenylamine (4-ADFA) through an intermediary preparation of 4-nitrodiphenylamine and/or 4-nitrosodiphenylamine and/or their salts in which aniline reacts with nitrobenzene in a liquid medium, whereby precursors of 4-ADFA are formed, i.e. 4-nitrosodiphenylamine (4-NODFA), 4-nitrodiphenylamine (4-NO2DFA) an/or their salts which, after hydrogenation, result in 4-ADFA.
4-aminodiphenylamine (4-ADFA) is widely used as an intermediate product in the production of alkylated derivatives having outstanding properties as antiozonants, antioxidants and stabilizers.
Present methods of industrial production of 4-ADFA start with hydrogenation of the intermediates, 4-NODFA or 4-NO2DFA. However, production of these intermediates, consisting in several technologically demanding steps, is accompanied by a number of side products, organic and inorganic waste which must be liquidated, this being one of the greatest problems of this production method.
Alternative methods of preparation of 4-ADFA intermediates which are ecologically and economically preferred consist in the direct reaction of aniline with nitrobenzene. The reaction is initiated by bases which form an anilide anion through the reaction which anion subsequently substitutes hydrogen in nitrobenzene by nucleophilic addition [A. Wohl et al., Ber. 34, 2442-2450, 1901; and A. Wohl, Ber. 36, 4135-4138, 1903], wherein if solid potassium hydroxide has been used as the base, mostly phenazine and phenazine oxide result, if sodium hydroxide has been used, also 4-NODFA is obtained.
In fifties, a number of authors have studied and described mechanism of the Wohl-Aue nucleophilic reaction of aniline and its derivatives with aromatic nitrocompounds by the action of bases (NaOH, KOH, eventually NaNH2) in the medium of benzene, toluene and xylene, wherein phenazine derivatives are formed. Besides them also further reaction products like 4-nitrosodiphenylamine, 4-nitrosubstituted diphenylamines, azobenzenes, azoxybenzenes [E. I. Abramova et al., Zhur. Obshchei Khim. 22, 502-509, 1953; S. B. Serebryanyi, Uspekhi Khimii 24, 313-345, 1955; S. B. Serebryanyi, Ukrain. Khim. Zhur. 21, 350-360, 1955; V. P. Chemetskii et al., Zhur. Obshchei Khim. 25, 2161-2170, 1955] have been isolated and decribed at the same time.
It is known [N. R. Ayyangar et al., Tetrahedron Letters 31, 3217-3220, 1990] that 4-NODFA and 4-NO2DFA arise by the reaction of nitrobenzene with acetanilide in the presence of dipolar aprotic solvent, dimethyl sulfoxide (DMSO), by the action of sodium hydroxide and potassium carbonate, as well as [A. A. Frimer et al., J. Org. Chem. 48, 1700-1705, 1983] that 4-NO2DFA arises with a yield of up to 24% by the reaction of aniline with nitrobenzene in the presence of bases, in this case of potassium butoxide or potassium peroxide in the medium of benzene and in the presence of a crown ether.
Similarly [D. J. Stuehr et al., J. Org. Chem. 50, 694-696, 1985], by the reaction of aniline and N-methylaniline in DMSO with potassium peroxide, together with 18-crown-6-ether, as well as with tertiary potassium butoxide a mixture of 4-NODFA, 4-NO2DFA, 4-ADFA, azobenzene, 4-phenylazodiphenylamine and phenylformamide has been obtained as the reaction product (no yields given).
Preparation of 4-ADFA through oxidation of aniline by ferricyanide in strongly alkaline medium is known [U.S. Pat. No. 4,760,186 and GB patent 1 440 767], wherein head-foot linking of two aniline molecules comes into effect, but with a low yield only.
U.S. Pat. No. 5,574,187 describes the 4-ADFA preparation by substitution of phenylhydroxylamine by aniline in the presence of an acidic catalyst. The product has been obtained with average yields only (max. of 51.2%).
Nature of the next U.S. Pat. No. 5,420,354 consists in the reaction of nitrobenzene with aniline in the presence of hydrogen, hydrogenation catalyst, acidic catalyst and hydrogenation inhibitor, which reaction yields directly 4-ADFA, but with relatively low yields (max. of 12%) and at a low selectivity of the reaction, similarly to other above given procedures.
In the EP application 566 783, the AKZO N.V. describes a method of manufacture of 4-nitrodiphenylamine by the reaction of nitrobenzene with aniline in the medium of a polar aprotic solvent, particularly dimethyl sulfoxide and tertiary butanol in a strongly alkaline reaction system, wherein hydroxides of alkali metals and of alkaline-earth metals, alkoxides, amides and hydrides of alkali metals have been used as bases, eventually in the presence of a phase transfer catalyst, like tetrabutylammonium hydrogen sulfate. Relatively high yields have been achieved, but selectivity of the reaction is insufficient. Therefore, it is necessary to isolate the product (NO2DFA) from the side products by crystallization. Moreover, in the process of products isolation salts are obtained, thus causing further costs for their processing. Also lossless recycling of bases and solvent mixtures back to the process is questionable.
A further halogen free method of 4-ADFA preparation consists in the reaction of aniline with 4-phenylazodiphenylamine in the presence of strong bases, like tertiary potassium butoxide with crown ethers or with quaternary ammonium hydroxides [U.S. Pat. Nos. 5,382,691, 5,633,407, 5,618,979 and 5,451, 702]. Subsequent transformation of 4-FADFA to 4-ADFA can be performed either by a catalytic hydrogenation according to the U.S. Pat. No. 5,451,702] or by a nucleophilic substitution reaction of 4-FADFA with amine in the presence of strong bases [U.S. Pat. Nos. 5,382,691, 5,633,407 and 5,618,979]. 4-ADFA can be also [see the U.S. Pat. Nos. 5,618,979 and 5,633,407 and the paper M. K. Stern et al., J. Org. Chem. 59, 5627-5632, 1994] prepared in one step directly by the reaction of azobenzene, eventually azoxybenzene, with aniline in the presence of strongly alkaline catalysts. However, in all above given procedures the starting raw material is azobenzene which is technically less easily accessible raw material, and it must be prepared in advance. Moreover, much waste arises which must be necessarily further treated or liquidated.
In a number of patents of the firm Monsanto [U.S. Pat. Nos. 5,117,063, 5,453,541, 5,608,111, 5,623,088], there is described a method of 4-ADFA intermediates production by direct reaction of aniline with nitrobenzene in an aprotic solvent with a controlled amount of a protic solvent by the action of bases, which include alkali hydroxides, alkoxides, hydrides and quaternary ammonium hydroxides with alkyl-, aryl- and aralkylsubstituents, as well as alkylsubstituted diammonium hydroxides. Nevertheless, the reaction products could be obtained with high yields and with high selectivity only when using quaternary ammonium hydroxides. Also mechanism of the reaction is known [M. K. Stern et al., J. Am. Chem. Soc. 114, 9237-9238, 1992, and New J. Chem. 20, 259-268, 1996].
From a comparison of the respective bases, described in the above given patents and papers, used in the reaction of aniline with nitrobenzene it becomes clear that the alkali hydroxides give low yields of the 4-ADFA intermediates. The yields increase substantially when alkali hydroxides are used together with crown ethers. Nevertheless, taking into account their technically demanding preparation, their industrial utilization is not very probable. Also the reaction in the presence of potassium butoxide and in the presence of DMSO shows low selectivity. Contrary to this, if quaternary ammonium hydroxides are used as bases in the reaction, both high selectivity and high yields are achieved. Nevertheless, they have a disadvantage of lower stability, they decompose in a concentrated state and, therefore, they must be stored in diluted aqueous solutions only. An another disadvantage is also their low thermal stability, they easily decompose at higher temperatures [A. Cope et al., Org. reactions, Vol. XI, p. 317, 1960; Hellman H., Angew. Chem. 65, 473-485,1953; F. Moller, Methoden der Organischen Chemie, Houben-Weyl XI/1, p.961-967, 262,1957, and XI/2, p.623, 631-640,1958].
In consequence of the effect of quaternary ammonium hydroxides on primary amines also their alkylation takes place easily. For example, tetramethylammonium hydroxide (TMAH) reacts with aniline, yielding N-methylaniline in an amount which depends on the reaction conditions chosen (U.S. Pat. No. 5,687,691). The N-methylaniline formed can hardly be separated from aniline, but this must be done before recycling aniline back to a further reaction cycle, so that no undesirable methylated derivatives of 4-ADFA arise as admixtures.
A disadvantage of quaternary ammonium hydroxides per se is also their technically demanding manufacture and their high price. Therefore, it is necessary in each cycle to isolate and recycle quaternary ammonium bases for the next production cycle what cannot be performed without lowering their activity.
The object of the present invention is to provide a solution which will utilize the advantages of known solutions, and will eliminate their disadvantages.
Nature of the present invention consists in a method of preparation of 4-aminodiphenylamine through an intermediate preparation of 4-nitrodiphenylamine and/or 4-nitrosodiphenylamine and/or their salts by the reaction of aniline with nitrobenzene in a liquid medium at a temperature of 50 to 130xc2x0 C., under normal or reduced pressure, in an inert atmosphere or in the presence of air oxygen, with subsequent hydrogenation of the intermediate of 4-nitrodiphenylamine and/or nitrosodiphenylamine and side products, and by isolation of 4-aminodiphenylamine and side products and recirculation of unconverted raw materials. The nature of the invention consists in that the reaction of aniline with nitrobenzene is performed in a reaction system, consisting of a true zwitterion salt solution with hydroxides of a general formula
HOxe2x88x92/(R1R2R3)N+xe2x80x94CHR4xe2x80x94(CH2)xxe2x80x94Yxe2x88x92/Z+
where R1 and R2 means methyl to dodecyl,
R3 means methyl, ethyl, phenyl, benzyl,
R4 means hydrogen or methyl
x means an integer of 0 to 5,
Yxe2x88x92 means CO2xe2x88x92, SO3xe2x88x92 and
Z+ means a cation of an alkali metal Na, K, Cs or a tetrasubstituted quaternary ammonium cation, like tetramethylammonium, or their mutual combinations, wherein the amounts of both the zwitterion salt and hydroxide are at least equimolar amounts related to the amount of nitrobenzene taken up in the reaction wherein 4-nitrosodiphenylamine and/or 4-nitrodiphenylamine arise, which yield after hydrogenation 4-ADFA, and after the reaction at least a half of the reaction system is recycled.
It has been found that it is preferable to perform the reaction in the presence of a true zwitterion salt solution with hydroxides of the general formula, where R1, R2 and R3 is methyl, R4 is hydrogen, x is 0, Yxe2x88x92 is CO2xe2x88x92, and Z+ is the potassium cation and/or a tetrasubstituted quaternary ammonium cation, and more preferably, Z+ represents the potassium cation and/or tetraalkylammonium cation having the number of carbons in the alkyl of 1 to 4.
The reaction medium can be formed separately and/or it will be formed in situ in the reaction system from the starting raw materials. The liquid medium for the reaction of aniline with nitrobenzene is formed by water and/or at least one organic compound, chosen from among aniline, pyridine, toluene, xylene, cyclohexane and aliphatic alcohols having the number of carbons in the molecule of 1 to 4.
An advantage of the present method consists mainly in that the reaction system according to this invention, used for the reaction, is technically more easily accessible and more stable than quaternary ammonium hydroxides and quaternary alkyldiammonium hydroxides themselves, while the reaction of aniline with nitrobenzene stays sufficiently selective for forming 4-ADFA intermediates (with a selectivity of at least 50% of 4-nitrodiphenylamine and nitrosodiphenylamine), and the resulting product is obtained with high yields.
One of the advantages of the process according to this invention is also technically accessible wide variety of bipolar to polypolar organic compounds, containing at least one nitrogen cation in their molecules, as well as their stability, not only thermal stability, but also stability under the hydrogenation conditions, and the fact that the reaction system can be regenerated.
It is known from the literature [M. Rabinowitz et al., Angew. Chem. 98, 958-968, 1986] that many organic reactions which are initiated by hydroxides take places under the conditions of the PTC/OHxe2x88x92 system, i.e. in the presence of phase transfer catalysts. Commonly used PTC are quaternary ammonium ions.
It is known as well that zwitterion salts have been used in several reactions as phase transfer catalysts, but in this case the assumed mechanism of the effect is different, because from the bipolar inner salt of the true zwitterion and hydroxide a bis-ionic pair arises [Starks, C. et al., Phase Transfer Catalysts Principles and Technique, N. Y. Acad. Press 1978, p. 67, 127, 365; Yu. Sh. Goldberg et al., Dokl. Akad. Nauk SSSR 294, 1387-1391, 1987; Yu. Sh. Goldberg et al., Zhur. Org. Khim. 23, 1561-1563, 1987; Yu. Sh. Goldberg et al., Tetrahedron 46, 1911-1922, 1990].
We designate as true zwitterions such compounds which contain in their molecule besides a carboxylic group also a perlakylated amino group, and these groups form mutually inner salts. These compounds do not contain any movable hydrogen, and they contain a quaternary ammonium group.
In the procedures, known from the literature, the zwitterion salts are used as phase transfer catalysts in a catalytic amount, namely in the amount of 1 to 5 mole %. Now it has been found that in the case of using the method of 4-ADFA intermediates preparation according to the present invention it is possible to achieve full conversion of nitrobenzene with aniline if the reaction is performed with at least equimolar amount of the zwitterion salt and hydroxide related to the amount of nitrobenzene, introduced to the reaction, thus indicating that the course of the reaction is different.
Zwitterion salts, known also as betaines or, eventually, sulfobetaines, are commercially available in the form of intramolecular salts or hydrated forms, or it is possible to prepare them according to procedures, known from the literature [Methoden der organischen Chemie (Houben-Weyl), X(12, p. 627-630, 1958; Ullmans Enzyklopxc3xa4die der technischen Chemie, Vol. 2, p. 497-498, Verlag Chemie 1982; Goldberg Yu. Sh. et al., Tetrahedron 46, 1911-1922, 1990; Goldberg Yu. Sh. et al., Dokl. Akad. Nauk SSSR 297, 1387-1391, 1987; Willstxc3xa4tter R., Ber. 35, 584-620-1907, U.S. Pat. No. 4,672,077 and Belg. patent 903 785].
In preparing the reaction system for condensation of aniline with nitrobenzene it is possible to proceed in such a way that a solution of hydroxide in a protic solvent (in water, in methanol or in 2-propanol) is prepared, and crystalline zwitterionic salt, possibly in the form of a hydrate, is added, and the corresponding solvent, for example aniline, is added to it. One can proceed also in such a way that aniline is added to a hydroxide solution in a protic solvent, and zwitterionic salt is added to this mixture. If preparing a reaction system, consisting of a mixture of hydroxides, one may proceed also in such a way that to a diluted aqueous solution of quaternary ammonium hydroxide crystalline zwitterionic salt is added, and after its dissolving solid alkali hydroxide, and finally aniline is added. It is also possible to prepare a methoxide solution by dissolving an alkali metal, its oxide or hydroxide in methanol, and adding a solution of the zwitterionic salt in aniline.
It is possible to vary the mutual ratios of the reaction components in a wide range in such a way, that the limiting component is either the zwitterion salt or nitrobenzene or aniline. Their mutual ratios may be chosen in such a way that the reaction will take place in an optimum, technologically and economically acceptable process.
The reaction may be performed in a wide range of temperatures from 50xc2x0 C. to 130xc2x0 C., depending on the reaction system used.
The reaction may be further performed in an inert atmosphere or under aerobic conditions, at the atmospheric pressure or at a reduced pressure, while the yield, conversion and selectivity of the reaction depend on the conditions chosen.
Further auxiliary protic and aprotic solvents may be used in the reaction, like tertiary butylalcohol, DMSO, diethyleneglycol dimethylether, ethyleneglycol monomethylether, toluene, xylene, cyclohexane, and so on.
The main products, obtained by the reaction, are 4-NODFA and 4-NO2DFA which are present in the reaction mixture in a free form or in the form of salts. Besides them and reaction water the reaction mixture may contain further substances, like 4-phenylazodiphenylamine, azobenzene, azoxybenzene, 2-nitrodiphenylamine, phenazine or phenazine oxide, depending on the choice of molar ratios of the reaction components of the system, as well as on the chosen type of zwitterions, their salts, on the protic solvent, possibly on the auxiliary solvent and their concentration in the reaction mixture, on temperature, reaction time and conversion degree of nitrobenzene. These facts are well known to experts in this field.
4-ADFA is obtained from the mixture of 4-NODFA, 4-NO2DFA and 4-phenylazodiphenylamine or their salts so, that the reaction mixture is after diluting by a solvent subjected to catalytic hydrogenation by known procedures.